Water Levels & Quality

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Water Levels

Click here for Current Lake Koronis water levels

The Minnesota Department of Natural Resources, Division of Waters has monitored Lake Koronis water levels in cooperation with volunteer readers since 1942. During the period of record the lake level has varied 6.0 feet based on 2,777 readings (through September 2009). In general, water levels decline from May through September, with the exception of a slight increase in mid-July in response to severe storms.

2010-2019 water levels

For more information about Lake Koronis water levels you can look at the Lake Management Plan.

Water Quality

Overall lake water quality can be summerized by three measurements.  These measurements are total phosphorus level, Chlorophyll-a level, and water transparency level which is usually measured by a Secci disc transparency test.

Generally, the more phosphorus there is in the lake the lower the water quality for recreation.  Phosphorus is food for plants and algae.  This means the more phosphorus there is in the lake, the more plants and algae will grow in the lake.  Phosphorus can enter the lake through runoff from agriculture, fertilized lawns, erosion, manure, improperly maintained septic systems, among other sources.

Since 1974, citizen volunteers from Rice Lake and Lake Koronis have participated in the Minnesota Pollution Control Agency’s (MPCA) Citizen Lake Monitoring Program (CLMP), recording secchi disc transparency – a measure of water clarity. For Koronis Lake, Roland Ebent, William H. Moyer, Jim Pater, Greg Berg, Harry Thielen, Garry Swenson, Mark Schmisek, and the North Fork Crow River Watershed District have been responsible for these efforts in recent years. On Rice Lake the volunteers Elaine Peterson, Pamela Bosshart, Roger & Karen Reede, Gary Skartvedt, Bob Vadner, Vince Miller, Mark Schmisek, Karl Dallas, and the Watershed District submitted transparency data.

On the Minnesota Pollution Control Agency’s web-site link, “Lake Water Quality Database,” additional water chemistry data is reported. The MPCA’s “Environmental Database Access” system also provides additional water chemistry data which includes total phosphorus concentrations, as well as other data.

RMB Environmental Labs website also has information about water quality in Lake Koronis and other lakes throughout the state.

One application of secchi disc transparency data is to convert the clarity measurements into a Carlson Trophic Status Index (TSI) score. The Carlson Trophic Status Index (TSI) is a tool used to summarize several measurements of water quality into one index value, which can be used to compare a lake to other lakes, or to historic/future data as a measure of degradation or improvement. In many ways, the index can be viewed as a measure of the potential for algae productivity. Since most people value lakes with low algae productivity, the lower the TSI value, the healthier the lake. Specifically:

TSI Range	Trophic Status	Characteristics
0-40	Oligotrophic	Clean Lake
41-50	Mesotrophic	Temporary algae & aquatic plant problems
50-70	Eutrophic	Persistent algae & aquatic plant problems
>70	Hyper-eutrophic	Extreme algae & aquatic plant problems

Over the past 3 decades yearly TSI averages have been taken of Koronis Lake.  Over that time Koronis Lake has had an average TSI level as low as 45.2 in 1989, and as high as 54.9 in 2001.  According to Koronis Lake’s Average TSI data from the Minnesota Pollution Control Agency(MPCA, Koronis Lake routinely exhibits conditions in the mesotrophic range, or eutrophic range.  The MPCA believes it is very important to attempt to lower the trophic status of lakes because a high trophic status can lead to Harmful Algae Blooms.

For more information about Lake Koronis water quality you can look at the Lake Management Plan

or Lake Koronis Lake Water Quality Summary.

Harmful Algae Blooms (HAB)

Most algae blooms are harmless, but some blue-green algal blooms can produce toxins that may sicken people and animals. Blue-green algae are found throughout Minnesota and thrive in warm, nutrient-rich lakes.

A major problem caused by these algae blooms is hypoxification (lowering of oxygen in the water) of lakes where these blooms occur.  This is caused when the algae die, sink to the bottom of the lake, and are consumed by aerobic (oxygen using) bacteria.  After a large algae bloom the bacteria can use up so much of the oxygen in the lake that it can cause fish kills.

In recent years this has been a serious problem for Tullibee in Koronis Lake.   Tullibee can only survive in cool (below 60 degrees Fahrenheit) water with oxygen levels above 5 parts per million.  Since 2000 Koronis has had several summers in which the water below 35 feet, which in the summer is the only part below 60 degrees F, had little to no oxygen.  This has caused a serious decline in the numbers of tullibee.  Tullibee are a major component in the diets of Northen Pike, Walley, and other game fish in Lake Koronis and if they continue to decline in numbers it will be just a matter of time before the game fish of Lake Koronis begin to decline as well.

If you would like to learn more about harmful algae blooms you can do so at the Minnesota Sea Grant web site.

Protecting Our Environment